The present invention relates to a rotary device for a horizontal injection molding machine for turning mold portions or molded articles between the mold mounting plates about a vertical axis. The invention also relates to an injection molding machine equipped with such a rotary device.
An apparatus for holding and turning molds or mold parts in a horizontal injection molding machine is known, for example, from U.S. Pat. No. 4,330,257 and European Pat. No. EP 0 922 556 A1, with the horizontal injection molding machine having mold mounting plates between which a turret (mold center platen) is slideable in longitudinal direction of the machine and provided as mold carrier with prismatic cross section which is supported for rotation about an axis extending perpendicular to the longitudinal axis of the machine. In order to shift the turret in longitudinal axis of the machine, on the one hand, and to rotate the turret about an axis extending perpendicular to the longitudinal axis of the machine, a system is provided in which the turret is rotatably supported in carriers, with the carriers slideably guided and supported at least on both lower tie bars of the injection molding machine (U.S. Pat. No. 4,330,257) or on all four tie bars (European Pat. No. EP 0 922 556 A1). To permit a precise guidance of the carrier and of the attached turret, support and guiding elements are required which are of highly precise construction and sized in narrow tolerances and which are arranged at great distances from one another as a result of the system. Thus, this support reacts sensitively to temperature fluctuations, i.e. during cool-down period and accompanying shrinkage, the clearance in the bearings increases whereas during heating period and accompanying expansion there is a risk that the support and guiding elements get jammed on the tie bars. To prevent the latter, the tolerances in the support and guiding elements should not be too narrow, i.e. sized not too precisely. A further drawback resides in the fact that the tie bars are loaded by a significant weight (inadmissible bending) depending on the design of the turret and the carriers, and that the torques encountered during rotation of the turret must be absorbed entirely by the tie bars, resulting in particular during starting and braking of the rotational movement in significant stresses.
It would therefore be desirable and advantageous to provide an improved rotary device for horizontal injection molding machines, obviating prior art shortcomings and ensuring a precise guidance along the longitudinal direction of the machine, on the one hand, while preventing a stress of the tie bars of the injection molding machine by additional weight or torques. It would further be desirable and advantageous to provide an improved injection molding machine, equipped with a precisely supported and guided rotary device in which the tie bars are not exposed to stress from the rotary device.
According to one aspect of the present invention, a rotary device includes a base plate supported on a machine bed of a horizontal injection molding machine; a rotary table supported on the base plate for rotation about a vertical axis; and drive means for rotating the rotary table.
According to another aspect of the present invention, a horizontal injection molding machine includes a machine bed defining a longitudinal axis; a first mold mounting plate fixedly secured onto the machine bed; a second mold mounting plate adapted for traveling relative to the first mold mounting plate; a rotary device arranged between the first and second mold mounting plates and including a base plate supported on the machine bed, a rotary table supported on the base plate for rotation about a vertical axis, and a drive mechanism for rotating the rotary table; and a shifting mechanism for displacing the rotary device in a direction parallel to the longitudinal axis.
The present invention resolves prior art problems by completely separating the guidance and the support of the rotary device from the tie bars. Thus, the tie bars are not unnecessarily exposed to stress, on the one hand, and the guidance and support can be dimensioned more precise compared to the prior art.
According to another feature of the present invention, the base plate has a substantially H-shaped, thereby establishing a stable support when the legs of the H-shaped base plate are sufficiently long, as well as allowing a simple withdrawal of the molded article into the free space between the legs of the H-shaped base plate. In connection with heavy mold center platens, it is advantageous to provide several linear guides and/or slideways and/or to so size the base plate as to reach to an area outside the zone of the mold mounting plates. By means of transport brackets and ring bolts, a complete stack mold can be dropped in closed state into the area between the mold mounting plates and mounted onto the rotary table, with centering elements being suitably provided for centering the center platen upon the rotary table.
An injection molding machine according to the present invention is characterized in particular by a simple mold assembly and disassembly, thereby simplifying and speeding-up the mold exchange. Moreover, the tie bars of such an injection molding machine are treated with care because the rotary device according to the invention is not guided and supported on the tie bars. Opening of the mold portions is advantageously supported by hydraulic release cylinders applying a separating pressure force in the partition planes between the mold center part and the stationary and moving mold portions.